The present invention relates to a method of manufacturing an orbiting scroll in a scroll fluid machine such as a scroll compressor, a scroll vacuum pump, a scroll expander or a scroll blower.
FIG. 6 shows a scroll fluid machine in which a fixed wrap 12 of a fixed scroll 11 engages with an orbiting wrap 16 of an orbiting scroll 15 rotatably connected to an eccentric axial portion 14 of a driving shaft 13. The orbiting scroll 15 is eccentrically revolved with respect to the fixed scroll 11 by the eccentric axial portion 14, thereby compressing a gas sucked through an air intake bore 17 as it moves toward a center. The rear surfaces of the scrolls 11, 15 have a plurality of cooling fins 18, 19 to release heat generated during operation.
The ends of the cooling fins 18 of the fixed scroll 11 are covered with a housing cover 20 to form a gas cooling path, while the ends of the cooling fins 19 of the orbiting scroll 15 are contacted with a bearing plate 23 which is rotatably mounted around the eccentric axial portion 14 via a bearing 21 and a bearing sleeve 22 to form a gas cooling path.
It is known that a predetermined compression or decompression is achieved by revolving the bearing plate 23 and the orbiting scroll 15 eccentrically by the eccentric axial portion 14.
To manufacture an orbiting scroll as described above, after working an orbiting scroll material and a bearing plate material separately, they are combined and the surfaces are treated.
As shown in a flow chart of FIG. 7, an orbiting scroll is manufactured by the steps “S” below:    S1: providing an orbiting scroll material;    S2: forming a plurality of cooling fins on the orbiting scroll material;    S3: providing a bearing plate material;    S4: forming a bearing bore in a bearing sleeve of the bearing plate material;    S5: aligning outer shapes of both the materials to combine them with a bolt and an adhesive;    S6: working an orbiting scroll with reference to the bearing bore;    S7: applying surface treatment on the combined materials; and    S8: obtaining a complete orbiting scroll.
However, such a method is disadvantageous in terms of productivity and precision of a product.
(a) Because an orbiting wrap is cut based on a bearing bore of the bearing plate material combined with the orbiting scroll material, positioning accuracy of the orbiting wrap depends on a position and precision of the bearing bore. As the position and precision of the bearing bore are not necessarily high order of accuracy, it is impossible to obtain products with high precision in micron order.
(b) Because the orbiting wrap is worked after combining the orbiting scroll material and the bearing plate material, handling and processing are difficult and workability is low.
(c) Surface treatment is applied after combining the orbiting scroll material having the cooling fins formed thereon and the bearing plate material having the bearing bore formed therein. Such surface treatment is not generally required for the bearing plate material, and unnecessary work and cost are involved.
(d) To cut the orbiting wrap after combining both materials, if one of the materials is found to be bad in quality or defective, it is difficult to take out only the material which is plastically deformed or has accumulated stress during the steps. Therefore, both the materials must be dumped together, which is uneconomical.